This invention pertains to the preparation of bis-(2-cyclopentenyl) ether from 2-cyclopentenyl carboxylates and/or 2-cyclopentenol as well as mixed ethers.
Bis-(2-cyclopentenyl) ether when epoxidized affords a commercial cycloaliphatic epoxide as described in U.S. Pat. No. 2,973,373. The use of this epoxy resin is described in U.S. Pat. No. 2,935,488.
Bis-(2-cyclopentenyl) ether was first synthesized by David et al. [Bull. Soc. Chim. France (5) 11, 5614 (1944)] employing the procedure shown below: ##STR1##
Several features of the above synthesis make it costly to conduct on a commercial scale. Expensive corrosion-resistant equipment is required in both steps because the process employs hydrogen chloride as a reactant and produces sodium chloride as a by-product. Chloride ion even in neutral or basic medium, causes severe pitting of stainless steel. Secondly stoichiometric amounts of both HCl and base are consumed which adds to the cost of the products. Thirdly malodorous by-products are formed contaminating the waste aqueous salt solution and producing unpleasant air-borne odors.
When one attempts to add a weak acid such as water or acetic acid to the double bond system of cyclopentadiene no formation of the desired 2-cyclopentenyl compound is observed, and the eventual sole product is dicyclopentadiene. This dimerization requires no catalyst.
When a strong acid other than anhydrous HCl or HBr is used, either in stoichiometric or catalytic amounts, a rapid polymerization of cyclopentadiene occurs.